Hydraulic systems such as fuel control systems use flow restrictors to control and/or balance the pressure drop and mass flow rate of a fluid flow through a fluid channel. Unfortunately, even after hydraulic systems are cleaned and filtered, there may be metal or dirt particulate in the hydraulic system that can clog an orifice of the flow restrictor, causing the hydraulic system to fail. Single-stage flow restrictors include a single orifice. Conventional multi-stage flow restrictors include a series of stacked discrete plates with multiple larger orifices. With a multi-stage flow restrictor, the fluid and particulate are channeled through the multiple larger orifices instead of through just one orifice, reducing fluid exit velocity, pressure, and heat as well as being more tolerant of particulate. Therefore, multi-stage flow restrictors enable larger orifices with the same resistance to flow as single-stage flow restrictors, while incurring less wear, lasting longer, and tolerating more particulate before flow is affected, resulting in more consistent and reliable flow restriction than provided by single-stage flow restrictors.
However, a conventional multi-stage flow restrictor requires precise machining in order to effect the desired flow restriction, making it expensive and difficult to manufacture. As a result, a conventional multi-stage flow restrictor represents a significant cost in the hydraulic system in which it is used. Costs are further compounded in the typical hydraulic system where a plurality of flow restrictors may be necessary. Furthermore, maintaining different sizes of conventional multi-stage flow restrictors on hand is necessary for compatibility with different fittings therefor, further increasing costs.
Hence, there is a need for flow restrictor assemblies with an improved multi-stage flow restrictor and methods for manufacturing the same. The flow restrictor assemblies and improved multi-stage flow restrictors are significantly more economical to manufacture than conventional flow restrictor assemblies and multi-stage flow restrictors and the multi-stage flow restrictors are customizable for different flow restriction thereby eliminating the need to keep different sizes on hand.